Continued investigation of the utility of ion-molecule reactions to distinguish between isomers of functionally substituted molecules will be studied using an ion cyclotron resonance spectrometer. There are several aspects of this study underwya, as follows: Use of sterically blocked molecules whose polarizabilities and dipole moments are available or easily calculated will be made to demonstrate that in series of compounds the classical formulas for ion-molecules reactions rates fail as steric hindrance to reaction increases. Epimeric compounds bearing different functional groups will be studied in order to ascertain the best conditions for reaction with ions from biacetyl to distinguish between epimers. New reagent ions and the optimization of conditions for distinguishing between epimers will be explored in general.